Technical Field
The present invention relates to the field of material technologies, and particularly to a layered oxide material, a preparation method, an electrode, a secondary battery and use.
Related Art
With the shortage of non-renewable energy resources including petroleum and coal and the exacerbation of environmental pollution, development of clean energy resources become a topic receiving great attention worldwide. A critical solution to this topic is to develop wind and solar energy resources and energy storage batteries provided therefor. The existing electrochemical energy storage devices mainly include lead-acid batteries, nickel-zinc batteries, nickel-hydrogen batteries, flow batteries and lithium-ion batteries, For most of the lithium-ion secondary batteries, a lithium-ion intercalation compound is used as a positive or negative electrode material, and a dry organic solvent is used as an electrolyte; and the lithium ions are reversibly deintercalated from the positive and negative electrode active material repeatedly without destroying the material structure. Lithium-ion batteries are generally accepted as the most promising power batteries for electric vehicles and energy storage batteries for renewable energy resources due to their high working voltage (3.6 V) (that is 3 times of that of nickel-cadmium and nickel-hydrogen batteries); small volume (that is 30% lower than nickel-hydrogen batteries); light weight (that is 50% lighter than nickel-hydrogen batteries); high specific energy (200 Wh/kg) (that is 2-3 times of that of nickel-cadmium batteries); lack of memory effect and pollution, low self discharge, and long cycling life. However, due to the limited lithium resources and the high extraction cost, the lithium-ion batteries are expensive, thus being failed to satisfy the low cost requirement in large-scale application. In contrast, the element sodium from the same main group has extremely similar physical and chemical properties to lithium, and has a higher abundance than lithium in the earth's crust and thus the cost of sodium-ion batteries is low. Therefore, development of sodium-ion secondary batteries as large-scale energy storage devices becomes a good choice.
In recent years, because of the limited lithium resources and the abundant sodium resources, sodiumion secondary batteries are extensively researched. At present, use of sodium as the electrode material of sodiumion batteries is reported in numerous literatures, in which the positive electrode material mainly includes Na3V2(PO4)3 having a NASCION-type structure [Electrochem. Commun., 2012, 14, 86-89, Adv. Energy Mater., 2013, 3, 156-160], NaVPO4, Na3V2(PO4)2F3[J. Mater. Chem., 2012, 22, 20535-20541], Na3V2O2(PO4)2F, and NaTi2(PO4)3. However, since such materials have a quite low electron conductivity and a poor kinetic performance, nanonization and carbon coating are frequently required to realize stable cycling. Moreover, the element vanadium contained therein is toxic, such that these materials have difficulty in practical application. A Na4Mn9O18 material with a tunnel structure is initially proposed by et al. [Adv. Mater., 2011, 23, 3155-3160], in which the movable sodium ions reside in an S-shaped large channel, Such a structure is quite stable during the whole cycle and can stand 2000 rounds of long cycles. However, the average voltage of the overall positive electrode material is low and the capacity is low because this structure mainly functions relying on the change from trivalent to tetravalent manganese, and the original sodium content is low.
Layered positive electrode material also receives great attention in recent years. P2-type NaxTMO2 and O3-type NaTMO2 are the mostly extensively studied materials [Physical B&C, 1980, 99, 81-85]. The O3-type material has a high sodium content in the O3 phase and a high charge capacity in initial cycle, but a poor electrochemical cycling performance and is sensitive to the air and water, such that it has difficulty in practical use. The P2-type material is highly stable during electrochemical cycle and has a fast deintercalation of sodium ions due to the large space where sodium ions reside. However, most of the P2-type materials are not stable in the air, and the charge capacity in initial cycle is generally low because the sodium content is low. In 2001, a P2-type Na2/3Ni1/3Mn2/3O2 material was prepared and characterized for its electrochemical performance by Lu et al, and was found to have a capacity of 160 mAh/g between 2.0-4.5V [Z. H. Lu and J. R. Dahn, J. Electrochem. Soc., 2001, 148A, 1225-A1229]. However, multiple plateaus appear on the electrochemical curve, and the cycling stability is extremely poor.
Moreover, the existing layered oxide cannot achieve a high charge capacity in initial cycle, a high efficiency, a high rate capability, and a good cycling performance unless nickel or cobalt is contained as a valence-variable element. However, the compounds containing the two elements are expensive, toxic, and undesirable for environment.